Transport Phenomena in a Physical World

Transport Phenomena in a Physical World Søren Prip Beier Download free books at Søren Prip Beier Transport Phenomena in a Physical World Download free eBooks at bookboon.com Transport Phenomena in a Physical World 2nd edition © 2015 Søren Prip Beier & bookboon.com ISBN 978-87-403-1124-2 Download free eBooks at bookboon.com Transport Phenomena in a Physical World Contents Contents Transport Phenomena in a Physical World Introduction Diferent kinds of transport 2.1 Difusivity, transport of mass 2.2 hermal conductivity, transport of energy 2.3 Dynamic viscosity, transport of momentum 10 2.4 Permeability, transport of volume 12 2.5 Electrical conductance, transport of electricity 14 Dimensionless numbers 16 Summary 17 www.sylvania.com We not reinvent the wheel we reinvent light Fascinating lighting offers an ininite spectrum of possibilities: Innovative technologies and new markets provide both opportunities and challenges An environment in which your expertise is in high demand Enjoy the supportive working atmosphere within our global group and beneit from international career paths Implement sustainable ideas in close cooperation with other specialists and contribute to inluencing our future Come and join us in reinventing light every day Light is OSRAM Download free eBooks at bookboon.com Click on the ad to read more Transport Phenomena in a Physical World Transport Phenomena in a Physical World Our physical world is changing, populations are growing, climate changes, new products are constantly being developed, new technologies and concepts emerge And we have even landed on Mars! All this calls for constant education, especially within natural science his book is written to you who have an interest in natural science and especially in understanding some basics within transport phenomena You either i) study to become or ii) works as a physicist, a chemist or an engineer As outline above: A lot is changing in our physical world but what is described in this book is not changing! It is not new! And I surely did not invent it! However, as the topics I will cover in this book gave me some fundamental insights into physics and transport phenomena when I was studying, my hope is that it will the same to you his book gives an overview of some analogies between these basic fundamentals: • Difusivity, D • hermal conductivity, k • Dynamic viscosity, μ • Permeability, Lp • Electrical conductance, σ hese terms are associated with the transport of mass, energy, momentum, volume and electrical charges (electricity) Many analogies can be extruded from these diferent phenomena which should be clear from reading this book Knowledge about transport phenomena in general is essential in many technologies I hope you will see and understand these analogies and beneit from it – just as I have done myself Understanding the basics is fundamental and a prerequisite for all development! September 2015 Søren Prip Beier Download free eBooks at bookboon.com Transport Phenomena in a Physical World Introduction Introduction hings only move when they are forced to move! A bicycle only moves when a force is applied in the form of pedaling A cloud on the sky only moves when a force is applied in the form of a storm or a wind Electrons only move in a power cable when a force is applied in the form of an electrical ield All sorts of transport only take place when a force, called a driving force, is applied Transport of mass, energy, momentum, volume, and electricity only takes place when a driving force is applied Transport is generally expressed as a lux J, which is deined by the amount of mass, energy, momentum, volume, or charges that are being transported pr area pr time he transport is proportional to the applied driving force and can be expressed by a linear phenomenological equation: J = - A˙ dX dx (1) In this book we are only dealing with one-dimensional cases where the transport is in the x-direction Analogies to two and three dimensional cases can be found in teaching books about transport phenomena he driving force is expressed as the gradient of X (concentration, temperature, velocity, pressure, or voltage) along the x-axis in the transport direction Since transport always goes “downhill” from high concentration, temperature, velocity etc to low concentration, temperature, velocity etc., a minus-sign is placed on the right side of the equation as the gradient dX/dx is negative and the lux should be positive he proportionality constant A is called a phenomenological coeicient and is related to many well known physical terms associated with diferent kinds of transport Table lists diferent kinds transport together with the driving forces, phenomenological lux equations, names of the phenomenological coeicients, units for the diferent luxes and the common name for the transport phenomena Table 1: Diferent kinds of transport Driving forces are speciied and lux equations are given for diferent kinds of transport SI units for the phenomenological coeicients and the luxes are given together with the common names for the diferent transport phenomena Download free eBooks at bookboon.com Transport Phenomena in a Physical World Diferent kinds of transport Diferent kinds of transport In the following sub sections the diferent kinds of transport listed in Table will be described 2.1 Difusivity, transport of mass Difusion of mass is also known as mass difusion, concentration difusion or ordinary difusion We are talking about molecular mass transport taking place as difusion of a component A through a medium consisting of component B he difusion coeicient DAB determines how fast the difusion takes place he subscript of the difusion coeicient indicates that the difusion is associated with the difusion of A through B A difusion situation is sketched in Figure for the difusion of a gas component A through a plate of silicone rubber (a) t